Hydrogen desorption from chemical vapor deposited diamond films

Temperature programmed desorption was used to measure the desorption kinetics of hydrogen and its isotopes from chemical vapor deposited diamond surfaces. The desorption spectra are surprisingly simple considering the polycrystalline nature of the sample, exhibiting a single peak at ∼1300 K for a heating rate of 6 K/s. There is no isotope effect to the desorption, and neither the position of the peak maximum nor the peak width change with increasing hydrogen coverage. The maximum surface coverage achieved is approximately one monolayer. The spectra can be represented by a single peak first order desorption model, yielding kinetic parameters of Ea=51 kcal/mol and ν=5×107 s−1. An alternate model of multiple desorption sites with a Gaussian-distributed population gives kinetic parameters of Ea,mean=82 kcal/mol, ν=9×1012 s−1, and σ (the width of the Gaussian distribution)=3 kcal/mol. A comparison to desorption from low-index natural diamond surfaces is presented.